St. Peter Canisius was a Jesuit theologian, defender of the Church during the reformation and is declared Doctor of the Church. He was born in Nijmegen, in the Netherlands and was educated at Cologne and Mainz, where he studied theology. In 1543, he joined the Society of Jesus (Jesuits) and returned to Cologne, where he founded a Jesuit community and was conspicuous in resisting the Protestant policies of Archbishop Hermann of Wied.

As his talents were recognized by the Jesuit Order, Peter was used as a teacher in Cologne, Vienna, and Ingolstadt; he also established Jesuit colleges in Munich, Innsbruck, Augsburg, Vienna, Wurzburg, and Dillingen. He soon acquired considerable renown for his preaching, his superb defense of Catholic doctrine and his resistance to Protestantism, especially in Bavaria, Bohemia, and parts of Austria.

Archduke Ferdinand of the Holy Roman Empire became Peter’s foremost patron, offering to him the prominent see of Vienna in 1552. Peter was commanded to decline the see by his superiors, as his considerable talents were needed elsewhere against Protestantism. Named provincial of Upper Germany in 1556, he took part in the Discussion at Worms (1557), the Council of Trent, and the Diet of Augsburg (1559). Peter concentrated on established colleges, promoting reform throughout Catholic lands, and halting the tide of the Protestant Reformation. Credit is given to him for revitalizing Catholicism in Austria and Germany at a time when they were in danger of being lost to Protestantism. For his achievements, he is honored as the Second Apostle of Germany.

A brilliant theologian, Peter was the author of several catechisms, the most famous being the Summa Doctrinae Christianae published in 1555. Presenting Catholic dogma through two hundred eleven questions and answers, the Summa was the chief writing of the Catholic Reformation (with the exception of the Spiritual Exercises) and was printed in some four hundred editions over the next two hundred years.

St. Peter Canisius is declared a Doctor of the Church which are certain men and women who are revered by the Church for the special value of their writings and preaching and the sanctity of their lives. They each made important and lasting contributions to the faith and are to be recognized for their great merits.

To be declared a Doctor of the Church, you have to meet three basic requirements.

1. First, you must have lived a life of exemplary holiness, or insignis vitae sanctitas (outstanding sanctity). In short, you have to be a saint.
   

2. Second, to be a Doctor of the Church you must have deepened the whole Church’s understanding of the Catholic Faith with emins doctrina (eminent teaching). Which is to say, sanctity isn’t enough. There are thousands of saints, but only 37 Doctors of the Church. To be a Doctor one must do more than just live the Faith. Rather, one must significantly and profoundly contribute to our understanding of Divine Revelation, helping us to know more deeply some truth about God and His actions in the World.
   

3. And third, a pope must officially declare you a Doctor. That being said, as the Church understands it, when a pope declares someone a Doctor of the Church, he’s not so much making someone a Doctor as he is recognizing what the Holy Spirit has already done - that He has conferred the charism of Doctor upon them.